The conventional flashlight employs a parabolic reflector to direct the light from the bulb to the object to be illuminated. When the bulb is at the focus of the paraboloid, all of the light rays leaving the bulb and impacting on the surface of the reflector will travel the same distance as they emerge parallel to the axis. The result is a bright concentrated spot beam. In order to form a broad beam with common flashlights, the light bulb is moved relative to the paraboloid so that the bulb is no longer at the focus. The result is that the light rays leaving the bulb reflect off of the parabolic surface and emerge diverging from the axis. The broad beam formed is less bright by at least the increase in the beam area over the spot. In addition, it will have an unilluminated spot at the center of the broad beam. This dark area is due to the light rays originating at a location other than the focus of the parabolic reflector. The resulting broad beam is much duller than the spot beam and there is a center area that is not illuminated.
It is an object of this invention to produce a spot beam that can be broadened to illuminate a wide area, but having no dark regions.
Yet another object of this invention is to produce a broad beam which has an apparent or perceived brightness that is greater than a beam which is attainable by existing techniques.